Medical science has long sought ways to minimize the dangers and trauma inherent in invasive surgical procedures. To this end, surgical techniques and instruments have been developed which, among other things, reduce the size of the incisions required to perform various surgical procedures. These techniques and instruments have been remarkably successful. Indeed, surgical procedures which only a few years ago would require an incision six or seven inches in length are today being performed through incisions which are less than one inch in length.
Trocars are one type of surgical instrument which have significantly contributed to these advances. In general, trocars are sharp, pointed surgical instruments which can be used to create and maintain small, hole-like incisions in a body cavity. Surgical instruments, including miniaturized optical devices, can be inserted through these small incisions and manipulated to perform surgical procedures within the body cavity without ever exposing the patient's internal organs or structures to the outside environment. Thus, by enabling the creation and maintenance of small working holes within a patient's body wall, conventional trocars have greatly contributed to the reduction in size of the incisions required to perform surgical procedures and reduced the related complications.
Conventional trocars generally include an obturator and a cannula. An obturator is a sharp, nail-like structure for penetrating a body wall to create a working channel into the body cavity. A cannula is a tube-like structure which can be inserted into the incision made by the obturator to maintain the working channel even after the obturator is removed. In the typical scenario, the obturator and cannula are assembled into a single unit (i.e., by inserting the obturator into the cannula) and then used to puncture the body wall. The obturator can then be carefully withdrawn from the cannula without removing the cannula from the body wall. Surgical instruments can be inserted through this cannula to perform an entire surgical procedure within the body cavity as mentioned above.
While conventional trocars plainly have many benefits, they also present significant hazards to both patients and medical personnel. For example, a patient is placed at risk of serious injury by the manner in which the trocar is employed. Specifically, in order to insert a trocar into a patient, a physician must overcome the resistance of the patient's body wall by exerting a significant amount of pressure on the trocar. When the obturator tip passes beyond the body wall the resistance suddenly reduces significantly. Thus, unless the physician immediately stops applying force, the trocar can move rapidly forward and possibly puncture or tear delicate internal organs. Since, the drop in resistance often occurs very suddenly, it can be very difficult to remove the force before injury occurs.
Medical personnel and patients are also placed at risk by the sharp tips of conventional trocars. Specifically, the sharp trocars make it very easy for medical personnel to inadvertently cut themselves or otherwise puncture their skin or gloves when using a conventional trocar. Not only are such accidental wounds painful, but they can also transfer the blood of the patient to the injured medical personnel or vice versa. With the increasingly widespread threat of HIV, the well-publicized AIDs virus, and other communicable diseases, the danger of accidental blood exchanges provides a clear danger to anyone involved with a conventional trocar. This is especially true when medical personnel are injured in a surgical setting since the patient's blood will likely be present when the accidental wound occurs. An accidental wound to a medical worker could, therefore, easily result in accidental blood exchanges between the injured party and the patient.
In addition to the serious risks detailed above, conventional trocars cause medical personnel many other problems. For instance, in many surgical procedures involving trocars, the body cavity is inflated with a non-toxic gas before the trocar is employed to create a working "pocket" or volume within the patient and to prevent the trocar from penetrating internal organs during insertion. For example, in an appendectomy, a patient's abdomen is first inflated with gas through a veress needle. The obturator is then used to place cannulas in various locations about the inflated abdomen for performing the procedure. One such cannula would typically be used to pass a small camera and light into the body cavity so a surgeon could view the operating area within the patient. Other cannulas would be used to pass surgical instruments into the cavity and remove tissue such as the appendix from the patient.
It is very important to maintain the abdomen of the patient in an inflated state throughout the procedure. To this end, conventional cannulas are often provided with sealing flap valves or the like which prevent gas from escaping from the patient's abdomen after the obturator is withdrawn. However, these sealing flap valves do not prevent gas leakage when a surgical instrument having a diameter which is smaller than the diameter of the cannula is employed. Instead, gas can easily pass through the gap between the inner wall of the cannula and the outer surface of the surgical instrument and deflate the work area. To prevent deflation of this type from occurring, physicians have often been required to utilize only those instruments whose dimensions closely match those of the cannula. This requirement inherently limits the surgeon's freedom of choice in selecting instruments for a procedure. Thus, while a certain instrument might be preferred by a physician, the physician might nonetheless be forced to use a less preferred (and possibly less effective) tool to perform a procedure to avoid deflating a body cavity.
Another problem conventional trocars present lies in the ease with which conventional cannulas can be inadvertently withdrawn from the working channel. Conventional cannulas typically include a smooth outer wall designed to facilitate insertion of the device through a body wall. The smooth surface of the cannula insures that the tissue surrounding the incision does not suffer excessive trauma when the cannula is passed through the body wall. Unfortunately, it also insures that the cannula can be withdrawn from the incision as smoothly and easily as it was inserted. This lack of resistance to withdrawal can easily result in the inadvertent withdrawal or removal of the cannula when an obturator or other surgical instrument is withdrawn. Inadvertent removals can create multiple problems, including deflation of the body cavity, splattering of body fluids, loss of time, and unnecessary trauma to the body tissue surrounding the working channel from the resulting multiple removals and insertions of the cannula.